R&D Report 1959-05 : Reception of Crystal Palace 51.5 Mc/s and 45.0 Mc/s channels in South Africa during the increasing phase of the sunspot cycle.
Reception reports have been received from the Panorama, Johannesburg receiving station of the. South African Broadcasting Corporation in respect of the reception there during the period 1000-1800 GMT of the Crystal Palace 41'5 Mc/s and 45'0 Mc/s frequencies and the data are here presented. The reports have been analysed for 28 months for 41'5 Mc/s and 21 months for 45'0 Mc/s. These frequencies are near the upper frequency limit for propagation by way of the F2 layer over a long path, even near sunspot maximum.
At the most favourable time of day and season reception of 41Â°5 Mc/s has occurred for up to 90% of the total time, and of 45'0 Mc/s for up to 58% of the total time. Marked seasonal variations in reception are found, resulting in a relatively large amount of reception during February-April, September-November and a relatively small amount during other months, which is in general accordance with the expected seasonal variations of MUF over the path. The mean monthly path MUF has been estimated, and, though this does not correlate well with the reception results in detail, it exhibits seasonal variations similar to those indicated by the reception results, except that during December-January the estimated MUF has a high value which is not confirmed by the results. A long period variation in reception is found which is not simply related to the increasing sunspot activity, but which may be due to a similar complex variation in the path MUF, the variations of which are determined by the magnitude and direction of variations in the two quantities FÂ° F2 and M4000, with increasing sunspot activity.